apply_footnote_plan can't differentiate between generic footnotes and source footnotes

[crystalluckett-sanofi]

Footnotes without a designated location are applied via gt::tab_source_note, which does not allow for generic footnotes to appear prior to footnotes with defined locations.

For example,

tfrmt <- tfrmt::tfrmt(
  label = label,
  column = column,
  param = param,
  body_plan = tfrmt::body_plan(
    tfrmt::frmt_structure(
      group_val = ".default",
      label_val = ".default",
      tfrmt::frmt_combine(
        "{count} {percent}",
        count = tfrmt::frmt("xxx"),
        percent = tfrmt::frmt_when(
          "==100" ~ tfrmt::frmt(""), 
          "==0" ~ "",
          "TRUE" ~ tfrmt::frmt("(xx.x%)")
        )
      )
    )
  )
) 
tfrmt::tfrmt(
  tfrmt,
  footnote_plan = tfrmt::footnote_plan(
    tfrmt::footnote_structure("BMI: Body Mass Index"),
    tfrmt::footnote_structure(
      "Placebo drug + standard of care",
      column_val = "column2"
    ),
    tfrmt::footnote_structure("Source Note")
  )
) |> 
  tfrmt::print_mock_gt()

This occurs because footnote structures without defined locations are automatically applied as source notes

tfrmt/R/apply_footnote_plan.R

Lines 45 to 47 in fe6960b

	if(length(loc$row)==0 && length(loc$col)==0){
	gt <- gt %>%
	tab_source_note(loc$note)

Whereas if I were to apply the footnotes to the gt object manually as desired, I can get the desired output:

tfrmt::print_mock_gt(tfrmt) |> 
  gt::tab_footnote("BMI: Body Mass Index") |> 
  gt::tab_footnote(
    "Placebo drug + standard of care",
    locations = gt::cells_column_labels(
      columns = all_of(
        as.character("column2")
      )
    )
  ) |> 
  gt::tab_source_note("Source Note")

I think a simple fix would be to add a new argument to footnote_structure, source, which is TRUE for source notes and FALSE otherwise.
When source == TRUE and there's no location, then call gt::tab_footnote. Otherwise, use gt::tab_source_note as is.